In case you run Siduction in VirtualBox
Kernel upgrade 4.18... to 4.19.0 ––> graphical environment does not work in VirtualBox
So keep a 4.18... kernel as fallback.
General suggestion for major kernel upgrades in VirtualBox:
# apt-mark hold linux-image-siduction-amd64
until the next upgrade of the virtualbox-guest-... packages drops in.